The present invention is directed to poly(arylene ether) copolymers, and in particular to poly(phenylene ether)-poly(organosiloxane) copolymers and methods for the synthesis thereof.
Poly(arylene) ethers, and in particular poly(2,6-dimethyl-1,4-phenylene) oxide, are engineering thermoplastics characterized by excellent hydrolytic stability, dimensional stability, and dielectric properties. Poly(arylene) ethers also possess high glass transition temperatures, on the order of greater than 200xc2x0 C., and high melt viscosity. Because of their high melt viscosity poly(arylene) ethers require high melt processing temperatures, which can lead to undesirable side-reactions such as degradation. Poly(arylene) ethers can also be brittle, and so are often blended with other polymers and copolymers.
Attempts to prepare blends, composites or copolymers of poly(arylene) ethers with poly(organosiloxane) polymers presents difficulties based on the extreme incompatibility of the poly(arylene) ether and poly(organosiloxane). Of these, methods for the preparation of copolymers of poly(arylene) ethers with poly(organosiloxane)s have been extensively investigated. A number of routes rely on activation of either the poly(arylene) ether or the poly(siloxane) moiety. For example, lithiation of a poly(arylene) ether followed by reaction with a chloro-terminated poly(organosiloxane) in solution leads to graft copolymers, as disclosed in JP 61,2525,214 to Matsui et al. This approach is prohibitively expensive for industrial production based on the costs of lithium reagents and the extremely pure conditions required for any solution lithiation process. Shea et al., in U.S. Pat. No. 4,814,392 report copolymer synthesis by reaction of anhydride-activated poly(arylene) ethers with an amino terminated poly(organosiloxane) in melt and in solution. The resulting copolymers are joined by either amide or imide linkages. Reaction of a hydroxy-terminated poly(arylene) ether with an amino-terminated poly(organosiloxane) is disclosed in U.S. Pat. No. 3,668,273 to Kranz et al. and U.S. Pat. No. 3,696,137 to Clark et al.
A reactive extrusion process has been used for preparation of poly(arylene) ether-poly(siloxane) copolymers from epoxy-, carboxy- or amino-functionalized poly(arylene) ethers with epoxy-, carboxy- or amino-functionalized poly(siloxane)s, in U.S. Pat. No. 5,385,984 to Blohm et al. Preparation of tri-block copolymers of poly(arylene ether)-poly(dimethylsiloxane)-poly(arylene ether) is disclosed by R. D. Allen and J. L. Hendrick, in Polym. Bull. Vol. 19, pp. 101-110 (1988). The copolymers were prepared based on phenolic hydroxyl-silylamine condensation via reaction of tertiary amino-stopped polydimethylsiloxane (PDMS) with the phenolic end groups of poly(arylene ether). These polymers are described as useful as additives for polystyrene-based materials.
Alternatively, U.S. Pat. No. 5,204,438 to Snow et al. and U.S. Pat. No. 5,281,686 to Blohm et al. disclose poly(arylene ether)-poly(organosiloxane) copolymers produced by incorporation of a silicon-containing phenol or bisphenol into a poly(arylene ether) chain by oxidative copolymerization with 2,6-xylenol. Graft co-polymers having up to about 20 mol % of poly(siloxane) may be prepared by this method. U.S. Pat. No. 5,357,022 to Banach et al. discloses formation of block copolymers by copolymerization of 2,6-xylenol with a phenol-stopped poly(siloxane) macromer. The macromer was prepared by hydrosilylation of an allylphenol derivative (e.g., eugenol, 2-methoxy-4-allyl-phenol) with dihydride-stopped polysiloxanes.
While suitable for their intended purposes, none of the preceding processes is cost-effective or suitable for industrial-scale preparation of poly(arylene ether)-poly(organosiloxane) copolymers. They use expensive reactants and/or preparation procedures, and the intermediates continue to exhibit thermal instability during processing. Accordingly, there remains a need in the art for methods for the industrially-feasible manufacture of poly(arylene ether)-poly(organosiloxane)copolymers having favorable processing characteristics, and which can be used as engineering thermoplastics, or which can be blended with poly(arylene) ethers or thermoset or rubber formulations to improve processing and other desirable properties such as flame retardancy and/or low smoke generation during burning.
The above-mentioned drawbacks and disadvantages are alleviated by a method for the synthesis of synthesis of poly(arylene ether)-poly(siloxane) copolymers, comprising
(a) synthesis of a poly(arylene ether) having the structure (1) 
wherein each Q1 is independently hydrogen, a primary or secondary alkyl group having from 1 to about 7 carbon atoms, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each Q2 is independently hydrogen, halogen, a primary or secondary alkyl group having from 1 to about 7 carbon atoms, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; Q3 is a hydrogen, a hydroxyl group, or a mixture thereof; and m is an integer having an average value in the range from about 3 to about 300;
(b) solution functionalization of polymer (1) to form functionalized poly(arylene ether) having the structure (2) 
wherein Q1, Q2, and m are as defined above; X is a reactive functional group selected from the group consisting of anhydride, hydroxyl, epoxy, carboxyl, xe2x80x94R1OH, R1CO2R2, xe2x80x94R1CH2xe2x95x90CH2, or vinyl, wherein R1 is a primary or secondary divalent alkyl or haloalkyl group having from 1 to 20 carbons, or an aryl group and R2 is a primary or secondary alkyl group having from 1 to 10 carbons; and Q4 is hydrogen, X, or a mixture thereof;
(c) reaction of functionalized poly(arylene ether) (2) with a poly(organosiloxane) having structure (3): 
wherein each R is independently a primary or secondary alkyl group having from one to 12 carbons, a primary or secondary haloalkyl group having from one to twelve carbons, an aryl group having from 6 to 12 carbons, an aralkyl group having from 7 to 18 carbons, or mixtures thereof; n is an integer having an average value from about 3 to about 500 inclusive; and A is a substituted or unsubstituted aromatic group having from 6 to about 18 carbon atoms, or a primary or secondary divalent saturated or unsaturated alkyl group having from 1 to about 30 carbon atoms; x is zero or one; and Y is a functional group reactive with X, selected from the group consisting of xe2x80x94OH, xe2x80x94CH2xe2x95x90CH2, epoxy, amino, carboxy, xe2x80x94C(O)CH2OH, or hydrogen, to form a poly(arylene ether)-poly(siloxane) copolymer; and
(d) isolation of the product poly(arylene ether)-poly(siloxane) copolymer, wherein the functionalization is in solution, and copolymer synthesis and isolation are effected by first solution and then melt copolymerization.
A further embodiment comprises a poly(arylene ether)-poly(siloxane) copolymer synthesized from a functionalized poly(arylene ether) wherein Q1, Q2, Q4, and X may be oriented in any of the available substitution positions on the aryl groups as generically indicated by structure (4): 
wherein Q1, Q2, Q4 X, and m are as defined above.
Another embodiment comprises a poly(arylene ether)-poly(siloxane) copolymer synthesized from a functionalized poly(arylene ether) (2) wherein Q1, Q2, and m are as defined above, and X is a reactive functional group selected from the group consisting of xe2x80x94R1OH, R1CO2R2, xe2x80x94R1CH2xe2x95x90CH2 or vinyl, wherein R1 is a primary or secondary divalent alkyl or haloalkyl group having from 1 to 20 carbons, an aryl group and R2 is a primary or secondary alkyl group having from 1 to 10 carbons; and a poly(organosiloxane) having the structure (2) wherein each of R, A, and x is as defined above, and Y is xe2x80x94OH or xe2x80x94C(O)CH2OH when X is xe2x80x94R1OH or R1CO2R2; Y is vinyl or allyl when X is vinyl or allyl; or Y is H and x is 0 when X is xe2x80x94R1CH 2xe2x95x90CH2 or vinyl. When Y is xe2x80x94OH or xe2x80x94C(O)CH2OH and X is xe2x80x94R1OH or R1CO2R2, reaction is conducted in the presence of a co-reactant selected from the group consisting of a dianhydride, diepoxide or dialkylcarbonate. When Y is vinyl or allyl and X is vinyl or allyl, reaction is initiated using heat or a free radical initiator. When Y is H and X is allyl or vinyl, copolymerization is conducted in the presence of a catalyst such as platinum.
The poly(arylene ether)-poly(siloxane) copolymers are useful as molding materials, as as treating agents for fillers such as fumed silica, quartz, or clays, or as sizing agents for glass, to promote compatibility between the polar surfaces of the filler and matrix. For example, fumed silica treated with poly(arylene ether)-poly(siloxane) copolymers are extremely useful for the manufacture of environmentally friendly tires, as the poly(arylene ether) portion of the copolymer is compatible with the styrene-butadiene rubber portion of the tire, while the poly(siloxane) portion of the copolymer has a very high affinity to the filler. The poly(arylene ether)-poly(siloxane) copolymers are also useful as additives to other thermoplastic or elastomeric resins. For example, linear poly(phenylene ether)-polyorganosiloxane copolymers in particular have use as impact modifiers or flame retardants for thermoplastic blends.
A method for synthesis of poly(arylene ether)-poly(siloxane) copolymers comprises reaction of a poly(arylene ether) having at least one functional group selected from the group consisting of anhydride, hydroxyl, epoxy, carboxyl, xe2x80x94R1OH, R1CO2R2, xe2x80x94R1CH2xe2x95x90CH2, allyl, or vinyl, wherein R1 is a primary or secondary divalent alkyl or haloalkyl group having from 1 to about 20 carbons, or an aryl group and R2 is a primary or secondary alkyl group having from 1 to about 10 carbons, with a poly(siloxane) have at least two functional groups reactive with the functional groups of the poly(arylene ether), the reactive groups of the poly(siloxane being selected from the group consisting of xe2x80x94OH, xe2x80x94CH2xe2x95x90CH2, epoxy, amino, carboxy, xe2x80x94C(O)CH2OH, and hydrogen. Preferably, the method comprises
(1) solution synthesis of a poly(arylene ether) having structure (1): 
(2) solution functionalization of poly(arylene ether) (1) to form functionalized poly(arylene ether) having the structure (2); 
(3) reaction of functionalized poly(arylene ether) (2) with a poly(organosiloxane) having structure (3): 
to form a poly(arylene ether)-poly(siloxane) copolymer; and
(4) isolation of the product poly(arylene ether)-poly(siloxane) copolymer, in a continuous process. In a particularly preferred embodiment, functionalization, copolymer synthesis, and isolation (steps 2, 3, and 4) are a continuous process effected by solution functionalization, solution co-polymerization, and devolatilization extrusion co-polymerization and isolation.
The first step, synthesis of poly(arylene ether)s (also known as polyphenylene ethers or polyphenylene oxides), is known, being described for example in U.S. Pat. Nos. 3,306,874 and 3,306,875, and 3,733,299, which are incorporated herein by reference. Preferred poly(arylene ethers) have the general structure (1) wherein each Q1 is independently halogen, a primary or secondary alkyl group having from 1 to about 7 carbon atoms, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; each Q2 is independently hydrogen, halogen, a primary or secondary lower alkyl group having from 1 to about 7 carbon atoms, phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and m is an integer having an average value in the range from about 3 to about 300. Exemplary lower alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-amyl, isoamyl, 2-methylbutyl, n-hexyl, 2,3-dimethylbutyl, 2-, 3-, or 4-methylpentyl and the corresponding heptyl groups; isopropyl, sec-butyl, and 3-pentyl. Preferably, Q1 is a primary alkyl radical having from 1 to about 4 carbon atoms, or phenyl. Most preferably, Q1 is methyl and Q2 is hydrogen.
Q3 in structure (1) is preferably a hydrogen, a hydroxyl, or a mixture thereof. As is well known by those of ordinary skill in the art, poly(phenylene ether)s having the general structure (1) generally comprise a mixtures of compounds, including both monohydroxyl and dihydroxyl-terminated polymers. Accordingly, a further embodiment uses a poly(arylene ether) wherein Q1, Q2, Q3, and the hydroxyl groups may be oriented in any of the available substitution positions on the aryl groups as generically indicated by structure (5): 
wherein Q1, Q2, Q3, and m are as defined above.
The ratio of monohydroxyl and dihydroxyl terminated polymers in structures (4) and (5) may be adjusted by variation in the reaction conditions by known methods, for example adjustment of the relative quantity of catalyst present during formation, e.g., TMDQ, wherein higher quantities of TMDQ result in higher relative quantities of dihydroxyl-terminated polymers. The particular molar ratio of monohydroxyl-terminated polymers to dihydroxyl-terminated polymers may be anywhere in the range of about 1:99 to about 95:5, preferably in the range of about 1:99 to about 50:50, more preferably in the range of about 1:99 to about 25:75, even more preferably in the range from about 1:99 to about 10:90.
Preferably, m has a value in the range from about 15 to about 200 or m is such that the poly(arylene ether)s generally have a number average molecular weight within the range of about 2,000-25,000 g/mol, preferably from about 2,000 to about 12,000, and a weight average molecular weight within the range of about 6,000-80,000, preferably from about 6,000 to about 60,000 as determined by gel permeation chromatography (GPC). Since many poly(siloxane)s degrade at the normal processing temperatures of poly(arylene ether)s (about 300xc2x0 C. or greater), preferred poly(arylene ether)s have a lower molecular weight and thus lower glass transition temperatures (less than about 200xc2x0 C.) to allow as low processing temperatures as possible (preferably below about 300xc2x0 C., and most preferably below about 250xc2x0 C.).
Both homopolymer and copolymer poly(arylene ether)s are included. The preferred homopolymers are those containing, for example, 2,6-dimethylphenylene ether units. Suitable copolymers include random copolymers containing, for example, such units in combination with 2,3,6-trimethyl-1,4-phenylene ether units or copolymers derived from copolymerization of 2,6-dimethylphenol with 2,3,6-trimethylphenol. Also included are poly(arylene ether)s containing moieties prepared by grafting vinyl monomers or polymers such as polystyrenes, as well as coupled poly(arylene ether)s in which coupling agents such as low molecular weight polycarbonates, quinones, heterocycles and formals undergo known reactions with the hydroxy groups of two poly(arylene ether) chains to produce a higher molecular weight polymer. Useful poly(arylene ether)s further include combinations of any of the above.
Poly(arylene ether)s are typically prepared by oxidative coupling of at least one corresponding monohydroxyaromatic compound. Particularly useful and readily available monohydroxyaromatic compounds are 2,6-xylenol (wherein each Q1 is methyl and each Q2 is hydrogen), whereupon the polymer may characterized as poly(2,6-dimethyl-1,4-phenylene ether), and 2,3,6-trimethylphenol (wherein each Q1 and one Q2 is methyl and the other Q2 is hydrogen). A variety of catalyst systems are known, generally containing at least one heavy metal compound such as copper, manganese or cobalt compound, usually in combination with various other materials. Preferred catalysts systems comprising copper compounds (e.g., cuprous or cupric ions, halide ions, and at least one amine) are described in U.S. Pat. Nos. 3,306,874, 3,306,875, 3,914,266, and 4,028,341, which are incorporated by reference herein. Manganese compounds are generally used in alkaline systems in which divalent manganese is present as complexes with one or more complexing and/or chelating agents such as dialkylamines, 0-hydroxyaromatic aldehydes, o-hydroxyazo compounds, and gamma-hydroxyimines.
Poly(arylene ether)s (1) (or (5) are then functionalized, preferably in solution, to form functionalized poly(arylene ether)s (2) or (4), respectively, wherein Q1, Q2, Q4, and m are as defined above. X is one of a number of reactive functional groups, selected from the group consisting of anhydride, hydroxyl, epoxy, carboxyl, xe2x80x94R1OH, R1CO2R2, xe2x80x94R1CH2xe2x95x90CH2, allyl, or vinyl, wherein R1 is a primary or secondary divalent alkyl or haloalkyl group having from 1 to about 20 carbons, or an aryl group and R2 is a substituted or unsubstituted primary or secondary alkyl group having from 1 to about 10 carbons. Again, preferred functionalized poly(arylene ether)s (2) have a lower glass transition temperature (less than about 200xc2x0 C.) to allow as a low processing temperature as possible (preferably below about 300xc2x0 C., and most preferably below about 250xc2x0 C.).
Functionalization is generally carried out by solution or co-extrusion methods. Methods for synthesis of a functionalized poly(arylene ether) (2) wherein X is anhydride, hydroxyl, epoxy, carboxyl, and allyl are known.
Reaction of poly(arylene ether) (1) with a compound having an acyl functional group yields a poly(arylene ether) (2) wherein X is an anhydride, for example, trimellitic anhydride acid as disclosed in U.S. Pat. No. 4,642,358, or maleic anhydride, as disclosed in U.S. Pat. No. 4,814,392, both of which are incorporated by reference herein.
Reaction of poly(arylene ether) (1) with a polymerizable epoxy-containing olefinic compound in the presence of a free radical initiator yields poly(arylene ether) (2) wherein X is an epoxy group. Epoxy- functionalized poly(arylene ether)s are disclosed in Brown et al., U.S. Pat. No. 4,9994,531, which is incorporated herein by reference. Epoxy-triazene capped poly(arylene) ethers are prepared by the reaction of a polyarylene ether and an epoxychlorotriazine, such as a diglycidyl chorocyanurate, as disclosed in U.S. Pat. No. 5,096,979, which is incorporated herein by reference.
Carboxy-functionalized poly(arylene ether)s are shown by Chalk et al. in J. Polymer Sci. Part A-1, Vol. 7, 691-705 (1969) and U.S. Pat. No. 4,646,708, both of which are incorporated by reference herein.
A preferred embodiment comprises functionalized poly(arylene ether)s (2) wherein X is a reactive functional group selected from the group consisting of xe2x80x94R1OH, R1CO2R2, xe2x80x94R1CH2xe2x95x90CH2, or vinyl, wherein R1is a primary or secondary divalent alkyl or haloalkyl group having from 1 to about 20 carbons, an aryl group and R2 is a primary or secondary alkyl group having from 1 to about 10 carbons.
Reaction of poly(arylene ether) (1) with glycidol yields poly(arylene ether) (2) wherein X is R1OH, as disclosed in U.S. Pat. No. 5,128,421 or hydroxyalkylation of poly(arylene ether) as described in U.S. Pat. No. 4,746,708.
Reaction of poly(arylene ether) (1) with fictionalizing compound having at least one carbon-carbon double or triple bond and at least one ester group yields poly(arylene ether) (2) wherein X is R1CO2R2, as disclosed in U.S. Pat. No. 4,888,397.
Reaction of poly(arylene ether) (1) an allylic halide under basic conditions yields poly(arylene ether) (2) wherein X allyl. Other methods for synthesis of poly(arylene ether)s (2) wherein X is allyl are disclosed in JP No""s. 5,078,470 or 5,306,366.
Reaction of poly(arylene ether) (1) with vinylbenzyl containing compounds yields poly(arylene ether) (2) wherein X is vinyl, as disclosed in U.S. Pat. No. 4,665,137.
Of the several synthetic methods used for poly(arylene ether) functionalization, poly(arylene ether) redistribution with functionalized phenolics is preferred, as disclosed by D. M. White, in Journal of Organic Chemistry, Vol. 34, p. 297 (1969) and in Journal of Polym. Science, Part A, Vol. 9, p. 663 (1971); and by H. A. M. van Aert, in Macromolecules, Vol. 28, 7967 (1995). Redistribution typically occurs between a poly(arylene ether) and a functionalized phenol in an inert solvent, for example chloroform, toluene, or the like, in the presence of an oxidizing agent such as a copper salt (for example copper nitrate trihydrate complex with N-methyl imidazole), a peroxide (for example benzoyl peroxide), or a quinone [for example 3,3xe2x80x2, 5,5xe2x80x2-tetramethyl4,4xe2x80x2-diphenquinone (TMDQ)]. Redistribution may be used to form poly(arylene ether)s wherein X is xe2x80x94COOH, vinyl, hydroxyalkyl, hydroxyaryl, or ester as, for instance, described in the U.S. Pat. No. 5,880,221.
After functionalization, the next step requires reaction of functionalized poly(arylene ether) (2) with a poly(organosiloxane) having structure (3): 
wherein each R is independently a primary or secondary alkyl group having from one to 12 carbons, a primary or secondary haloalkyl group having from one to twelve carbons, an aryl group having from 6 to 12 carbons, an aralkyl group having from 7 to 18 carbons, or mixtures thereof. Preferably, R is methyl. Preferably, n is an integer having an average value from about 1 to about 1,000,000 inclusive, more preferably n is an integer having an average value in the range from about 1 to about 100,000 inclusive and most preferably, n is an integer having an average value in the range from about 3 to about 500 inclusive.
In the above formula (3), A is a substituted or unsubstituted aromatic group having from 6 to about 18 carbon atoms, or a primary or secondary divalent saturated or unsaturated alkyl group having from 1 to about 30 carbon atoms; x is zero or one; and Y is a functional group reactive with X, selected from the group consisting of xe2x80x94OH, xe2x80x94CH2xe2x95x90CH2, epoxy, amino, carboxy, xe2x80x94C(O)CH2OH, or, when x is zero, hydrogen. Reaction of (2) with (3) forms a poly(arylene ether)-poly(siloxane) copolymer. The amount of poly(siloxane) (3) used for copolymerization is in the range from about 1 to about 80, preferably from about 5 to about 50, and most preferably from about 10 to about 30 mole percent based on the amount of poly(arylene ether) monomer units. Use of more than about 5 percent by weight of poly(siloxane) results in lubrication of the screw during extrusion, which can adversely affect the extrusion and/or molding process. This difficulty is reduced by performing the copolymerization in solution and, for instance, a CSTR type of reactor.
Various initiators may be used to facilitate copolymerization. For example, tertiary amines such as imidazoles, quaternary onium salts such as tetramethylammonium chloride, or mineral acids such as hydrochloric acid may be present for catalysis of the reaction of a carboxy-modified poly(arylene ether) (2) wherein X is xe2x80x94COOH, with an epoxy-modified poly(siloxane) (2) wherein Y is an epoxy group.
One preferred siloxane (3) has X substituted by the reactive functional groups xe2x80x94OH, xe2x80x94C(O)CH2OH, or xe2x80x94OH wherein x 1 and A is a substituted or unsubstituted alkyl or aryl group, when X is xe2x80x94OH or xe2x80x94CO2R2. In these instances, reaction is conducted in the presence of a co-reactant selected from the group consisting of a dianhydride, for example 1,2,4,5-tetracarboxylic anhydride benzene, a diepoxide, for example a diglycidyl ether of bisphenol A, or a dialkylcarbonate, for example dibutylcarbonate. Where significant differences in reactivity exists, reaction is conducted stepwise, e.g., a diaryl carbonate may first be reacted with a hydroxyalky-substituted poly(siloxane), followed by reaction of the formed intermediate with a hydroxy-stopped poly(arylene ether). Alternatively, a hydroxy-stopped polyarylene ether) may first be reacted with a hydroxyalkyl-substituted poly(siloxane), followed by reaction of the formed intermediate with a hydroxy-stopped poly(siloxane). Various esterification catalysts suitable for use in these reactions are known in the art, and include, for example ammonium salts such as tetraalkyl ammonium halides or phosphonium salts such as tetraalkylphosphonium halides.
Another preferred siloxane (3) is substituted by the reactive functional groups vinyl or allyl when X is hydroxy, vinyl or allyl. Copolymerization is initiated using heat or a free radical initiator, for example peroxides such as dicumylperoxide. Grafting may occur on poly(arylene ether) methyl groups and/or irregular units composed of bonds sensitive to a radical reaction (particularly where X is hydroxy). Grafting to vinyl-poly(siloxane)s can be further facilitated by using poly(arylene ether) functionalized with an unsaturated bond such as vinyl or allyl group.
Still another preferred siloxane (3) is a hydrido-substituted siloxane wherein Y is hydrogen and x is 0 when X is xe2x80x94R1CH2xe2x95x90CH2 or vinyl. Other polyorganosiloxanes having at least two Sixe2x80x94H groups are also useful. Copolymerization can be conducted in the presence of a catalyst such as platinum or palladium.
The above-described steps of poly(arylene ether) synthesis, functionalization, and copolymerization may occur in solution, in the melt, or a combination thereof Prior art processes have generally required isolation of each intermediate after each step. Various isolation techniques are available for the separation of poly(arylene ether)s, their functionalized derivatives, and their copolymers after synthesis. In a preferred embodiment, synthesis, functionalization, copolymer formation and the product isolation steps occur via an in-line process without isolation of the intermediates.
Accordingly, after the poly(arylene ether) solution synthesis step(s), the resulting poly(arylene ether) solution is transferred to a modification vessel where solution functionalization and solution copolymer formation occurs sequentially. The solution containing the copolymer is then treated to effect isolation of the copolymer. The final isolation of the poly(arylene ether)-poly(siloxane) copolymer is preferably carried out in a devolatilizing extruder although other methods involving precipitation, spray drying, wiped film evaporators, flake evaporators, and flash vessels with melt pumps, including various combinations involving these methods are also useful and in some instances preferred. In these techniques it is highly preferred that catalysts (e.g., metal catalysts) removal be completed in the prior process steps as any catalyst remaining in solution will necessarily be isolated in the poly(arylene ether)-poly(siloxane) copolymers.
Devolatilizing extruders and processes are known in the art and typically involve a twin-screw extruder equipped with multiple venting sections for solvent removal. The devolatilizing extruders most often contain screws with numerous types of elements adapted for such operations as simple feeding, devolatilization and liquid seal formation. These elements include forward-flighted screw elements designed for simple transport, and reverse-flighted screw and cylindrical elements to provide intensive mixing and/or create a seal. Particularly useful are counterrotating, non-intermeshing twin screw extruders, in which one screw is usually longer than the other to facilitate efficient flow through the die of the material being extruded. Such equipment is available from various manufacturers including Welding Engineers, Inc.
In a preferred embodiment, isolation comprises pre-concentration (partial evaporation of the solvent) and devolatilization extrusion steps. During pre-concentration, the major part of the solvent is removed by evaporation, preferably at an elevated temperature, for example in the range from about 150 to about 300xc2x0 C., more preferably in the range from about 180 to about 260xc2x0 C., and/or elevated pressure, for example in the range from about 2 to about 75 bar, more preferably in the range from about 5 to about 50 bar. Pre-concentration is followed by devolatilization extrusion to remove the residual solvent.
As an alternative to completely isolating the poly(arylene ether)-poly(siloxane) copolymer, one or more resins may be added to the devolatilized poly(arylene ether)-poly(siloxane) copolymer in the same process. The one or more resins may be fed into the devolatilizing extruder although additional extruders may also be used. Possible variations include melt feeding the one or more resins into the devolatilizing extruder or melt feeding the poly(arylene ether)-poly(siloxane) copolymer from the devolatilizing extruder into a second compounding extruder as well as combinations of these. The one or more resins can vary widely and can also include additives common to such compatibilized blends. Such additives include impact modifiers, lubricants, flame retardants, pigments, colorants, fillers, reinforcing agents, carbon fibers and fibrils, and the like.
In a particularly preferred embodiment, functionalization, copolymer synthesis, and isolation (steps 2,3, and 4) are a continuous process effected by solution functionalization, solution co-polymerization at low temperature followed by solution polymerization at high temperature and pressure, and finally melt copolymerization. Preferably, melt polymerization and isolation of the copolymer are performed by devolatilization. The sequence of low and high temperature solution co-polymerization, followed by devolatilization extrusion serves to increase the degree of copolymer formation.
Accordingly, after poly(arylene ether) synthesis, a solution of the poly(arylene ether) (1) is treated so as to result in solution functionalized poly(arylene ether (2). Solvents for effective functionalization are known, for example inert solvents such as chloroform, toluene, and chlorobenzene. Toluene is preferred.
Solution copolymer formation is next initiated. Solution copolymerization is generally effected at temperatures in the range from about 20 to about 300xc2x0 C., and at pressures in the range from about 1 to about 100 bar. Reaction times vary depending on the reactants, temperature, and pressure, but are typically in the range from about 0.1 to about 50 hours.
Preferably, solution co-polymerization occurs in two steps, a first, low temperature, low pressure step, and a second, higher temperature and/or higher pressure step. The low temperature step is preferably in the range from about 20 to about 100xc2x0 C., and preferably at about 60 to about 100xc2x0 C. Pressure is preferably in the range from about 1 to about 1.2 bar. The second solution copolymerization is at a higher temperature and/or pressure, preferably in the range from about 150 to about 350xc2x0 C., and more preferably in the range from about 200 to about 300xc2x0 C. Pressure is in the range from about 2 to about 100 bar, and preferably in the range from about 10 to about 50 bar. Precise temperatures and pressures will depend at least on part on the reactants.
Solution copolymerization is then preferably followed by melt copolymerization, and finally isolation of the copolymer. Melt copolymerization and isolation are most preferably performed simultaneously by devolatilization extrusion co-polymerization. This step is preferably performed at temperatures in the range from about 150 to about 350xc2x0 C., using a screw speed in the range from about 50 to about 1000 rpm and residence time in the range from about 10 seconds to about 15 minutes. A high degree of copolymer formation occurs in some instances during a single extrusion step. This indicates that the conversion to poly(arylene ether)-poly(siloxane) copolymer initiated in the solution steps can be further increased in the extrusion step.
The above-described processes are suitable for the formation of poly(arylene ether)-poly(siloxane) copolymers from poly(arylene ether)s (1) wherein X is a hydroxy, carboxy, ester, hydroxyalkyl, vinyl, amino, or allyl group, and reactive poly(siloxane)s (2) wherein Y is an epoxy, amino, hydroxy, vinyl, hydroxyalkyl, hydroxyaryl, hydroxyacyl, or allyl group.
Another embodiment comprises the copolymeric reaction product of a vinyl-modified poly(arylene ether) (2) wherein X is vinyl, with a vinyl stopped poly(siloxane) (3), wherein Y is vinyl. Since copolymerization is by a free radical mechanism, a mixture of block and graft copolymers is generally produced.
Another embodiment comprises the copolymeric reaction product of a hydroxyalkyl-modified poly(arylene ether) (2) wherein X is a hydroxyalkyl, with a hydroxyalkyl- or hydroxyaryl-stopped poly(siloxane) (3), wherein x is 1, A is an alkyl or aryl group, and Y is a hydroxy group. Copolymerization in this case occurs in the presence of a co-reactant as discussed above.
Another embodiment comprises the copolymeric reaction product of an ester-modified poly(arylene ether) (2) wherein X is a carboxy ester group, with a with a hydroxyalkyl- or hydroxyaryl-stopped poly(siloxane) (3), wherein Y is a hydroxyalkyl or hydroxy aryl group. Block copolymers result where X is an end group as shown in (2). Formation of graft copolymers occurs when X is present along the poly(arylene ether) chain.
A still further embodiment comprises poly(arylene ether)-polyorganosiloxane copolymers produced by hydrosilation of an allyl-functionalized poly(arylene ether) wherein X is allyl, with a hydride-containing poly(organosiloxane) wherein x is 0 and Y is hydrogen. Linear block copolymers are produced from poly(arylene ether)s (2) having allylic groups at the terminus of the polymer chains. For generation of linear block copolymers poly(arylene ether)s containing 1 to 2 allylic functions and polyorganosiloxanes containing 1 to 2 Sixe2x80x94H groups per polymer chain are preferred. Alternatively, if poly(arylene ether)-polyorganosiloxane graft copolymers are desired, poly(arylene ether)s containing grafted allylic functions are used. These materials may be prepared by known routes including metallation of a poly(arylene ether) with an organolithium (as described above by Chalk) followed by allylation of the poly(arylene ether) with an allyl halide. Such allylated poly(arylene ether)s are also described by Ishii, et al in Microelectronics Technology, Chapter 32, pg. 485-503. For the generation of crosslinked poly(arylene ether)-polyorganosiloxane at least one of a poly(arylene ether) containing greater than 2 allylic groups per molecule or polyorganosiloxane containing greater than 2 Sixe2x80x94H groups per molecule is used.
The block copolymers may be formulated with one or more other fillers or additives to further modify their properties. Typical examples of such additives include flame retardants, plasticizers, flow promoters, inorganic fillers, or other thermoplastic resins including poly(phenylene ether)s or siloxanes or thermosetting resins such as epoxies, polyesters, maleimides or cyanate esters.
The poly(arylene ether)-poly(siloxane) copolymers are useful as molding materials, for example as resins for electrical applications, including encapsulants or resins for printed circuit board laminates the copolymers may further be used as as treating agents for fillers such as fumed silica, quartz, particulate glass, or clays, or as sizing agents for glass, to promote compatibility between the polar surfaces of the filler, e.g., the silanol groups of glass), and the polymeric matrix. For example, fumed silica treated with poly(arylene ether)-poly(siloxane) copolymers are extremely useful for environmentally benign tire applications, as the poly(arylene ether) portion of the copolymer is compatible with the styrene-butadiene rubber portion of the tire, while the poly(siloxane) portion of the copolymer has a very high affinity to the filler.
The poly(arylene ether)-poly(siloxane) copolymers are also useful as additives to other thermoplastic or elastomeric resins. For example, linear poly(phenylene ether)-polyorganosiloxane copolymers in particular have use as impact modifiers or flame retardants for thermoplastic blends. When used as additives for poly(arylene ether) resins, the resulting blends generally have better or comparable properties, such as impact strength and/or flame retardancy and/or low smoke generation under burning.
The invention is further illustrated by the following non-limiting examples.